Titan, the one place in the Solar System where the Titanic could have cruised with impunity

PIA17655 Kraken Mare cropPretty much everywhere on Earth where there is liquid water there is life. The biochemistry that powers our cells only runs in liquid water. In the Universe liquids are rare, like Little Red Riding Hood liquids are very particular, requiring conditions that are neither too hot nor too cold. Much of the Universe is near 0 K (-273 C), which is way too cold, or inside in stars at thousands of degrees, which is way too hot. Saturn’s moon Titan is at a refreshing – 180 C, which is too cold for liquid water, but methane is liquid at this temperature. The image to the left is of the surface of Titan and the dark regions are huge lakes of liquid methane and ethane.

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Are less active chromosomes like WD40?

PLoSBiol3.5.Fig1bNucleus46ChromosomesWe all have 46 chromosomes worth of DNA in each of our cells. Each one is kind of a stringy object that is typically around a few micrometres across, and all 46 are squeezed into a cell nucleus that is itself maybe only 7 micrometres across. These chromosomes are surprisingly variable. Chromosome number 18 has maybe 250 genes on it, while number 19 has around 1,500 genes, despite being around the same size*. So chromosome 19 is a lot more active than 18, many more proteins are being made from its much larger number of genes.

It has been known for a long time that the chromosomes are not uniformly distributed in the nucleus. The active ones, the ones like chromosome 19 with many genes, tend to be nearer the centre, while the quieter ones are near the edge. You can see this in image and schematic at top left, the less active chromosome 18 is at the bottom near the right end, while the more active chromosome 19 is above it and so away from the edge. The image is a from a paper by Bolzer et al.

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Video

Using analogy to understand how chameleons change colour

The video shows artificial models of the key structures in a type of cell called a melanophore. This is from a nice paper by Aoyama et alMelanophores and similar cells are how animals like chameleons change colour. The blobs that show up as bright here in the fluoresence microscopy images are actually dark brown under natural conditions. They contain eumelanin, the brown pigment that makes brown hair brown.

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